Xen and the Art of Consolidation
Tom
Eastep
2006
2007
Thomas M. Eastep
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation; with
no Invariant Sections, with no Front-Cover, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
GNU Free Documentation
License
.
This article applies to Shorewall 3.0 and later. If you are running
a version of Shorewall earlier than Shorewall 3.0.0 then please see the
documentation for that release.
Xen Network Environment
Xen is a
paravirtualization tool that allows you to run
multiple virtual machines on one physical machine. It is available on a
wide number of platforms and is included in recent
SUSE distributions.
Xen refers to the virtual machines as
Domains. Domains are numbered with the first domain
being domain 0, the second domain 1, and so on. Domain 0
(Dom0) is special because that is the domain
created when the machine is booted. Additional domains (called
DomU's) are created using the xm
create command from within Domain 0. Additional domains can also
be created automatically at boot time by using the
xendomains service.
Xen virtualizes a network interface named eth0
This assumes the default Xen configuration created by
xend and assumes that the host system has a single
Ethernet interface named eth0.
in each domain. In Dom0, Xen also creates a bridge (xenbr0) and a number of virtual interfaces
as shown in the following diagram.
![]()
I use the term Extended Dom0 to distinguish
the bridge and virtual interfaces from Dom0 itself. That distinction is
important when we try to apply Shorewall in this environment.
The bridge has a number of ports:
peth0 — This is the port that connects to the physical network
interface in your system.
vif0.0 — This is the bridge port that is used by traffic to/from
Domain 0.
vifX.0 — This is the bridge port that is used by traffic to/from
Domain X.
Before Xen
Prior to adopting Xen, I had a home office crowded with 5 systems,
three monitors a scanner and a printer. The systems were:
Firewall
Public Server in a DMZ (mail)
Private Server (wookie)
My personal Linux Desktop (ursa)
My work system (docked laptop running Windows XP).
The result was a very crowded and noisy room.
After Xen
Xen has allowed me to reduce the noise and clutter considerably. I
now have three systems with two monitors. I've also replaced the
individual printer and scanner with a Multifunction
FAX/Scanner/Printer.
The systems now include:
Combination Firewall/Public Server/Private Server/Wireless
Gateway using Xen (created by building out my Linux desktop
system).
My work system.
My Linux desktop (wookie, which is actually the old public
server box)
Most of the Linux systems run SUSE 10.1; my
personal Linux desktop system and our Linux Laptop run
Ubuntu "Dapper Drake".
The configuration described below uses a
bridged Xen Networking configuration; if you want to see how to accomplish
a similar configuration using a Routed Xen configuration then please see
this article. I am now using the
routed configuration because it results in one fewer domains to
administer.
Here is a high-level diagram of our network.
![]()
As shown in this diagram, the Xen system has three physical network
interfaces. These are:
eth0 -- connected to the
switch in my office. That switch is cabled to a second switch in my
wife's office where my wife has her desktop and networked printer (I
sure wish that there had been wireless back when I strung that CAT-5
cable halfway across the house).
eth1 -- connected to our
DSL "Modem".
eth2 -- connected to a
Wireless Access Point (WAP) that interfaces to our wireless
network.
There are three Xen domains.
Dom0 (DNS name ursa.shorewall.net) is used as a local file
server (NFS and Samba).
The first DomU (Dom name firewall, DNS name gateway.shorewall.net) is
used as our main firewall and wireless gateway.
The second DomU (Dom name lists, DNS name lists.shorewall.net) is used as
a public Web/FTP/Mail/DNS server.
Shorewall runs in Dom0 and in the firewall domain.
As the developer of Shorewall, I have enough experience to be very
comfortable with Linux networking and Shorewall/iptables. I arrived at
this configuration after a fair amount of trial and error
experimentation. If you are a Linux networking novice, I recommend that
you do not attempt a configuration like this one for your first
Shorewall installation. You are very likely to frustrate both yourself
and the Shorewall support team. Rather I suggest that you start with
something simple like a standalone
installation in a domU; once you are comfortable with that then
you will be ready to try something more substantial.
As Paul Gear says: Shorewall might make iptables easy,
but it doesn't make understanding fundamental networking principles,
traffic shaping, or multi-ISP routing any easier.
The same goes for Xen networking.
Domain Configuration
Below are the relevant configuration files for the three domains.
I use partitions on my hard drives for DomU storage devices.
/boot/grub/menu.lst — here is the entry
that boots Xen in Dom0.
title XEN
root (hd0,1)
kernel /boot/xen.gz dom0_mem=458752 sched=bvt
module /boot/vmlinuz-xen root=/dev/hda2 vga=0x31a selinux=0 resume=/dev/hda1 splash=silent showopts
module /boot/initrd-xen
/etc/modprobe.conf.local
eth1 (PCI 00:09.0) and
eth2 (PCI 00:0a.0) are
delegated to the firewall DomU where they become eth3 and eth4 respectively. The SUSE 10.1 Xen
kernel compiles pciback as a module so the instructions for PCI
delegation in the Xen Users Manual can't be followed directly (see
http://wiki.xensource.com/xenwiki/Assign_hardware_to_DomU_with_PCIBack_as_module).
options pciback hide=(00:09.0)(00:0a.0)
install tulip /sbin/modprobe pciback ; /sbin/modprobe --first-time --ignore-install tulip
options netloop nloopbacks=1
/etc/xen/auto/01-firewall — configuration
file for the firewall domain
# -*- mode: python; -*-
# configuration name:
name = "firewall"
# usable ram:
memory = 384
# kernel and initrd:
kernel = "/xen2/vmlinuz-xen"
ramdisk = "/xen2/initrd-xen"
# boot device:
root = "/dev/hdb2"
# boot to run level:
extra = "3"
# network interface:
vif = [ 'mac=aa:cc:00:00:00:02, bridge=xenbr0', 'mac=aa:cc:00:00:00:03, bridge=xenbr1' ]
# Interfaces delegated from Dom0
pci=[ '00:09.0' , '00:0a.0' ]
# storage devices:
disk = [ 'phy:hdb2,hdb2,w' ]
/etc/xen/auto/02-lists — configuration file
for the lists domain
# -*- mode: python; -*-
# configuration name:
name = "lists"
# usable ram:
memory = 512
# kernel and initrd:
kernel = "/xen2/vmlinuz-xen"
ramdisk = "/xen2/initrd-xen"
# boot device:
root = "/dev/hda3"
# boot to run level:
extra = "3"
# network interface:
vif = [ 'mac=aa:cc:00:00:00:01, bridge=xenbr1' ]
hostname = name
# storage devices:
disk = [ 'phy:hda3,hda3,w' ]
With all three Xen domains up and running, the system looks as
shown in the following diagram.
![]()
The zones correspond to the Shorewall zones in the firewall DomU
configuration.
If you want to run a simple NAT gateway in a Xen DomU, just omit
the second bridge (xenbr1), the second delegated interface, and the
second DomU from the above configuration. You can then install the
normal Shorewall two-interface sample
configuration in the DomU.
Under some circumstances, UDP and/or TCP communication from a
domU won't work for no obvious reason. That happened with the
lists domain in my setup. Looking at
the IP traffic with tcpdump -nvvi eth1 in the
firewall domU showed that UDP packets
from the lists domU had incorrect
checksums. That problem was corrected by arranging for the following
command to be executed in the lists
domain when its eth0 device
was brought up:
ethtool -K eth0 tx off
Under SUSE 10.1, I placed the following in
/etc/sysconfig/network/if-up.d/resettx (that file
is executable):
#!/bin/sh
if [ $2 = eth0 ]; then
ethtool -K eth0 tx off
echo "TX Checksum reset on eth0"
fi
Under other distributions, the technique will vary. For example,
under Debian or Ubuntu,
you can just add a 'post-up' entry to
/etc/network/interfaces as shown here:
iface eth0 inet static
address 206.124.146.177
netmask 255.255.255.0
post-up ethtool -K eth0 tx off
Update. Under SUSE 10.2, communication from a domU works okay
without running ethtool but traffic shaping in
dom0 doesn't work! So it's a good idea to run it just to be
safe.
SUSE 10.1 includes Xen 3.0.2 which supports PCI delegation. The
network interfaces that connect to the net and wifi zones are delegated
to the firewall DomU.
When Shorewall starts during bootup of Dom0, it creates the two
bridges using this /etc/shorewall/init extension
script:
for bridge in xenbr0 xenbr1; do
if [ -z "$(/sbin/brctl show 2> /dev/null | fgrep $bridge)" ]; then
/sbin/brctl addbr $bridge
/sbin/ip link set dev $bridge up
fi
done
Dom0 Configuration
The goals for the Shorewall configuration in Dom0 are as
follows:
Allow traffic to flow unrestricted through the two bridges.
This is done by configuring the hosts connected to each bridge as a
separate zone and relying on Shorewall's implicit intra-zone ACCEPT
policy to permit traffic through the bridge.
Ensure that there is no stray traffic between the zones. This
is a "belt+suspenders" measure since there should be no routing
between the bridges (because they don't have IP addresses).
The configuration is a simple one:
/etc/shorewall/zones:
#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall
loc ipv4
dmz ipv4
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
/etc/shorewall/policy (Note the unusual use
of an ACCEPT all->all policy):
#SOURCE DEST POLICY LOG LIMIT:BURST
# LEVEL
dmz all REJECT info
all dmz REJECT info
all all ACCEPT
#LAST LINE -- DO NOT REMOVE
/etc/shorewall/interfaces:
#ZONE INTERFACE BROADCAST OPTIONS
loc xenbr0 192.168.1.255 dhcp,routeback
dmz xenbr1 - routeback
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/rules:
#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/
# PORT PORT(S) DEST LIMIT GROUP
#SECTION ESTABLISHED
#SECTION RELATED
SECTION NEW
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Firewall DomU Configuration
In the firewall DomU, I run a conventional three-interface
firewall with Proxy ARP DMZ -- it is very similar to the firewall
described in the Shorewall Setup
Guide with the exception that I've added a fourth interface for
our wireless network. The firewall runs a routed OpenVPN server to provide road warrior access
for our two laptops and a bridged OpenVPN server for the wireless
network in our home. Here is the firewall's view of the network:
![]()
The two laptops can be directly attached to the LAN as shown above
or they can be attached wirelessly -- their IP addresses are the same in
either case; when they are directly attached, the IP address is assigned
by the DHCP server running in Dom0 and when they are attached
wirelessly, the IP address is assigned by OpenVPN.
The Shorewall configuration files are shown below. All routing and
secondary IP addresses are handled in the SUSE network
configuration.
/etc/shorewall/shorewall.conf:
STARTUP_ENABLED=Yes
VERBOSITY=0
LOGFILE=/var/log/firewall
LOGFORMAT="Shorewall:%s:%s:"
LOGTAGONLY=No
LOGRATE=
LOGBURST=
LOGALLNEW=
BLACKLIST_LOGLEVEL=
MACLIST_LOG_LEVEL=$LOG
TCP_FLAGS_LOG_LEVEL=$LOG
RFC1918_LOG_LEVEL=$LOG
SMURF_LOG_LEVEL=$LOG
LOG_MARTIANS=No
IPTABLES=/usr/sbin/iptables
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin
SHOREWALL_SHELL=/bin/bash
SUBSYSLOCK=
MODULESDIR=
CONFIG_PATH=/etc/shorewall:/usr/share/shorewall
RESTOREFILE=standard
IPSECFILE=zones
IP_FORWARDING=On
ADD_IP_ALIASES=No
ADD_SNAT_ALIASES=No
RETAIN_ALIASES=No
TC_ENABLED=Internal
CLEAR_TC=Yes
MARK_IN_FORWARD_CHAIN=Yes
CLAMPMSS=Yes
ROUTE_FILTER=No
DETECT_DNAT_IPADDRS=Yes
MUTEX_TIMEOUT=60
ADMINISABSENTMINDED=Yes
BLACKLISTNEWONLY=Yes
DELAYBLACKLISTLOAD=No
MODULE_SUFFIX=
DISABLE_IPV6=Yes
BRIDGING=No
DYNAMIC_ZONES=No
PKTTYPE=No
RFC1918_STRICT=Yes
MACLIST_TTL=60
SAVE_IPSETS=No
MAPOLDACTIONS=No
FASTACCEPT=Yes
BLACKLIST_DISPOSITION=DROP
MACLIST_TABLE=mangle
MACLIST_DISPOSITION=DROP
TCP_FLAGS_DISPOSITION=DROP
/etc/shorewall/zones:
#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall
net ipv4 #Internet
loc ipv4 #Local wired Zone
dmz ipv4 #DMZ
vpn ipv4 #Open VPN clients
wifi ipv4 #Local Wireless Zone
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
/etc/shorewall/policy:
#SOURCE DEST POLICY LOG LIMIT:BURST
# LEVEL
$FW $FW ACCEPT
$FW net ACCEPT
loc net ACCEPT
$FW vpn ACCEPT
vpn net ACCEPT
vpn loc ACCEPT
loc vpn ACCEPT
$FW loc ACCEPT
wifi all REJECT $LOG
loc $FW REJECT $LOG
net $FW DROP $LOG 1/sec:2
net loc DROP $LOG 2/sec:4
net dmz DROP $LOG 8/sec:30
net vpn DROP $LOG
all all REJECT $LOG
#LAST LINE -- DO NOT REMOVE
/etc/shorewall/params (edited):
MIRRORS=<comma-separated list of Shorewall mirrors>
NTPSERVERS=<comma-separated list of NTP servers I sync with>
POPSERVERS=<comma-separated list of server IP addresses>
LOG=info
INT_IF=eth0
DMZ_IF=eth1
EXT_IF=eth3
WIFI_IF=eth4
OMAK=<IP address at our second home>
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
/etc/shorewall/init:
echo 1 > /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_be_liberal
/etc/shorewall/interfaces:
#ZONE INTERFACE BROADCAST OPTIONS
net $EXT_IF 206.124.146.255 dhcp,norfc1918,logmartians,blacklist,tcpflags,nosmurfs
dmz $DMZ_IF 192.168.0.255 logmartians
loc $INT_IF 192.168.1.255 dhcp,routeback,logmartians
wifi $WIFI_IF 192.168.3.255 dhcp,maclist
vpn tun+ -
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/nat:
#EXTERNAL INTERFACE INTERNAL ALL LOCAL
# INTERFACES
206.124.146.178 $EXT_IF 192.168.1.3 No No #Wookie
206.124.146.180 $EXT_IF 192.168.1.6 No No #Work LapTop
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
/etc/shorewall/masq (Note the cute trick here and in
the following proxyarp file that allows me to
access the DSL "Modem" using its default IP address
(192.168.1.1)). The leading "+" is required to place the
rule before the SNAT rules generated by entries in
/etc/shorewall/nat above.
#INTERFACE SUBNET ADDRESS PROTO PORT(S) IPSEC
+$EXT_IF:192.168.1.1 0.0.0.0/0 192.168.1.254
$EXT_IF 192.168.0.0/22 206.124.146.179
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
/etc/shorewall/proxyarp:
#ADDRESS INTERFACE EXTERNAL HAVEROUTE PERSISTENT
192.168.1.1 $EXT_IF $INT_IF yes
206.124.146.177 $DMZ_IF $EXT_IF yes
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tunnels:
#TYPE ZONE GATEWAY GATEWAY
# ZONE
openvpnserver:udp net 0.0.0.0/0 #Routed server for RoadWarrior access
openvpnserver:udp wifi 192.168.3.0/24 #Home wireless network server
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/actions:
#ACTION
Mirrors # Accept traffic from Shorewall Mirrors
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
/etc/shorewall/action.Mirrors:
#TARGET SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE
# PORT PORT(S) DEST LIMIT
ACCEPT $MIRRORS
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/rules:
SECTION NEW
###############################################################################################################################################################################
#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/
# PORT PORT(S) DEST LIMIT GROUP
###############################################################################################################################################################################
REJECT:$LOG loc net tcp 25
REJECT:$LOG loc net udp 1025:1031
#
# Stop NETBIOS crap
#
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
#
# Stop my idiotic work laptop from sending to the net with an HP source/dest IP address
#
DROP loc:!192.168.0.0/22 net
###############################################################################################################################################################################
# Local Network to Firewall
#
DROP loc:!192.168.0.0/22 fw # Silently drop traffic with an HP source IP from my XP box
ACCEPT loc fw tcp 22
ACCEPT loc fw tcp time,631,8080
ACCEPT loc fw udp 161,ntp,631
ACCEPT loc:192.168.1.5 fw udp 111
DROP loc fw tcp 3185 #SUSE Meta pppd
Ping/ACCEPT loc fw
REDIRECT loc 3128 tcp 80 - !206.124.146.177
###############################################################################################################################################################################
# Road Warriors to Firewall
#
ACCEPT vpn fw tcp ssh,time,631,8080
ACCEPT vpn fw udp 161,ntp,631
Ping/ACCEPT vpn fw
###############################################################################################################################################################################
# Road Warriors to DMZ
#
ACCEPT vpn dmz udp domain
ACCEPT vpn dmz tcp www,smtp,smtps,domain,ssh,imap,https,imaps,ftp,10023,pop3 -
Ping/ACCEPT vpn dmz
###############################################################################################################################################################################
# Local network to DMZ
#
ACCEPT loc dmz udp domain
ACCEPT loc dmz tcp ssh,smtps,www,ftp,imaps,domain,https -
ACCEPT loc dmz tcp smtp
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# Internet to ALL -- drop NewNotSyn packets
#
dropNotSyn net fw tcp
dropNotSyn net loc tcp
dropNotSyn net dmz tcp
###############################################################################################################################################################################
# Internet to DMZ
#
ACCEPT net dmz udp domain
ACCEPT net dmz tcp smtps,www,ftp,imaps,domain,https -
ACCEPT net dmz tcp smtp - 206.124.146.177,206.124.146.178
ACCEPT net dmz udp 33434:33454
Mirrors net dmz tcp rsync
Limit:$LOG:SSHA,3,60\
net dmz tcp 22
Trcrt/ACCEPT net dmz
##############################################################################################################################################################################
#
# Net to Local
#
# When I'm "on the road", the following two rules allow me VPN access back home using PPTP.
#
DNAT net loc:192.168.1.4 tcp 1729
DNAT net loc:192.168.1.4 gre
#
# Roadwarrior access to Wookie
#
ACCEPT net:$OMAK loc tcp 22
Limit:$LOG:SSHA,3,60\
net loc tcp 22
#
# ICQ
#
ACCEPT net loc:192.168.1.3 tcp 113,4000:4100
#
# Bittorrent
#
ACCEPT net loc:192.168.1.3 tcp 6881:6889,6969
ACCEPT net loc:192.168.1.3 udp 6881:6889,6969
#
# Skype
#
ACCEPT net loc:192.168.1.6 tcp 1194
#
# Traceroute
#
Trcrt/ACCEPT net loc:192.168.1.3
#
# Silently Handle common probes
#
REJECT net loc tcp www,ftp,https
DROP net loc icmp 8
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net udp domain,ntp
ACCEPT dmz net tcp echo,ftp,ssh,smtp,whois,domain,www,81,https,cvspserver,2702,2703,8080
ACCEPT dmz net:$POPSERVERS tcp pop3
Ping/ACCEPT dmz net
#
# Some FTP clients seem prone to sending the PORT command split over two packets. This prevents the FTP connection tracking
# code from processing the command and setting up the proper expectation. The following rule allows active FTP to work in these cases
# but logs the connection so I can keep an eye on this potential security hole.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# Local to DMZ
#
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,rsync,https,imaps,ftp,10023,pop3,3128
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# DMZ to Local
#
ACCEPT dmz loc:192.168.1.5 udp 123
ACCEPT dmz loc:192.168.1.5 tcp 21
Ping/ACCEPT dmz loc
###############################################################################################################################################################################
# DMZ to Firewall -- ntp & snmp, Silently reject Auth
#
ACCEPT dmz fw tcp 161,ssh
ACCEPT dmz fw udp 161
REJECT dmz fw tcp auth
Ping/ACCEPT dmz fw
###############################################################################################################################################################################
# Internet to Firewall
#
REJECT net fw tcp www,ftp,https
DROP net fw icmp 8
ACCEPT net fw udp 33434:33454
ACCEPT net:$OMAK fw udp ntp
ACCEPT net fw tcp auth
ACCEPT net:$OMAK fw tcp 22
Limit:$LOG:SSHA,3,60\
net fw tcp 22
Trcrt/ACCEPT net fw
###############################################################################################################################################################################
# Firewall to DMZ
#
ACCEPT fw dmz tcp domain,www,ftp,ssh,smtp,https,993,465
ACCEPT fw dmz udp domain
REJECT fw dmz udp 137:139
Ping/ACCEPT fw dmz
##############################################################################################################################################################################
# Avoid logging Freenode.net probes
#
DROP net:82.96.96.3 all
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tcdevices
#INTERFACE IN-BANDWITH OUT-BANDWIDTH
$EXT_IF 1300kbit 384kbit
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tcclasses#INTERFACE MARK RATE CEIL PRIORITY OPTIONS
$EXT_IF 10 5*full/10 full 1 tcp-ack,tos-minimize-delay
$EXT_IF 20 3*full/10 9*full/10 2 default
$EXT_IF 30 2*full/10 6*full/10 3
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/tcrules#MARK SOURCE DEST PROTO PORT(S) CLIENT USER TEST
# PORT(S)
1:110 192.168.0.0/22 $EXT_IF #Our internal nets get priority
#over the server
1:130 206.124.146.177 $EXT_IF tcp - 873 #Throttle rsync traffic to the
#Shorewall Mirrors.
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
The tap0 device used by the bridged OpenVPN server is bridged to
eth0 using a SUSE-specific SysV init script:
#!/bin/sh
#
# The Shoreline Firewall (Shorewall) Packet Filtering Firewall - V3.0
#
# This program is under GPL [http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt]
#
# (c) 1999,2000,2001,2002,2003,2004,2005 - Tom Eastep (teastep@shorewall.net)
#
# On most distributions, this file should be called /etc/init.d/shorewall.
#
# Complete documentation is available at http://shorewall.net
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of Version 2 of the GNU General Public License
# as published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
# If an error occurs while starting or restarting the firewall, the
# firewall is automatically stopped.
#
# Commands are:
#
# bridge start Starts the bridge
# bridge restart Restarts the bridge
# bridge reload Restarts the bridge
# bridge stop Stops the bridge
# bridge status Displays bridge status
#
# chkconfig: 2345 4 99
# description: Packet filtering firewall
### BEGIN INIT INFO
# Provides: bridge
# Required-Start: boot.udev
# Required-Stop:
# Default-Start: 2 3 5
# Default-Stop: 0 1 6
# Description: starts and stops the bridge
### END INIT INFO
################################################################################
# Interfaces to be bridged -- may be listed by device name or by MAC
#
INTERFACES="eth0"
#
# Tap Devices
#
TAPS="tap0"
################################################################################
# Give Usage Information #
################################################################################
usage() {
echo "Usage: $0 start|stop|reload|restart|status"
exit 1
}
#################################################################################
# Find the interface with the passed MAC address
#################################################################################
find_interface_by_mac() {
local mac
mac=$1
local first
local second
local rest
local dev
/sbin/ip link ls | while read first second rest; do
case $first in
*:)
dev=$second
;;
*)
if [ "$second" = $mac ]; then
echo ${dev%:}
return
fi
esac
done
}
################################################################################
# Convert MAC addresses to interface names
################################################################################
get_interfaces() {
local interfaces
interfaces=
local interface
for interface in $INTERFACES; do
case $interface in
*:*:*)
interface=$(find_interface_by_mac $interface)
[ -n "$interface" ] || echo "WARNING: Can't find an interface with MAC address $mac"
;;
esac
interfaces="$interfaces $interface"
done
INTERFACES="$interfaces"
}
################################################################################
# Start the Bridge
################################################################################
do_start()
{
local interface
get_interfaces
for interface in $TAPS; do
/usr/sbin/openvpn --mktun --dev $interface
done
/sbin/brctl addbr br0
for interface in $INTERFACES $TAPS; do
/sbin/ip link set $interface up
/sbin/brctl addif br0 $interface
done
}
################################################################################
# Stop the Bridge
################################################################################
do_stop()
{
local interface
get_interfaces
for interface in $INTERFACES $TAPS; do
/sbin/brctl delif br0 $interface
/sbin/ip link set $interface down
done
/sbin/ip link set br0 down
/sbin/brctl delbr br0
for interface in $TAPS; do
/usr/sbin/openvpn --rmtun --dev $interface
done
}
################################################################################
# E X E C U T I O N B E G I N S H E R E #
################################################################################
command="$1"
case "$command" in
start)
do_start
;;
stop)
do_stop
;;
restart|reload)
do_stop
do_start
;;
status)
/sbin/brctl show
;;
*)
usage
;;
esac